Draw a rectangle on track vehicles

Im working in a little program who have the capacity to track vehicles. Now I can track but I want to draw a rectangle over each car. How can I do it? Could some one lend me a hand or give me some advice. Thank you so much in advice team.

I just try to learn by examples of internet and do it something that works. It's obvious that i'm not a master-python but, I want to create a little project who can track vehicles and then count it. I just go step by step...Thanks mate.

if it's so, you could try to get a homography from the 2 point sets, and do a backprojection, -- the outliers are the moving things (against the camera's movement, -- well, more or less..) ! see e.g. here

Vote my post! :D I cant vote up the responses. It's a nice idea and thank you so much @supra56 for comment. The main problem is that I want to put a circle or a square o rectangle... around the cars some bounding box may be? I'm still thinking about solution... because I think that it's possible to do.
Now, I have the corners of the cars with ShiTomasy and I just want a bounding box who can track these points across the frame. thank you, Im open to new ideas and advices thank you so much.